css - undefined method `attr' for nil:NilClass (NoMethodError) -


i have method in cli app giving me error.

the method is:

def self.deal_page(input, product_url)     self.open_deal_page(input)     deal = {}     html = open(@product_url)     doc = nokogiri::html(html)     data = doc.text.strip     deal[:name] = doc.css("h1").text.strip     deal[:discription] = doc.css(".textdescription").text.strip     @purchase_link = nil     @purchase_link= doc.at_css("div.detailleftcolumn a.success").attr("href")         if @purchase_link.nil?          deal[:purchase] = @product_url        else          deal[:purchase] = @purchase_link        end      deal   end

and error is:

/home/himachhag-45739/code/popular-deals-from-slickdeals.net-cli/lib/popular_deals/newdeals.rb:54:in `deal_page': undefined method `attr' nil:nilclass (nomethoderror)          /home/himachhag-45739/code/popular-deals-from-slickdeals.net-cli/lib/popular_deals/cli.rb:70:in `disply_deal'                                                          /home/himachhag-45739/code/popular-deals-from-slickdeals.net-cli/lib/popular_deals/cli.rb:49:in `menu'                                                                 /home/himachhag-45739/code/popular-deals-from-slickdeals.net-cli/lib/popular_deals/cli.rb:9:in `call'                                                                  /home/himachhag-45739/code/popular-deals-from-slickdeals.net-cli/bin/popular-deals:10:in `<top (required)>'                                                            /usr/local/rvm/gems/ruby-2.3.1/bin/popular-deals:22:in `load'                                                                                                          /usr/local/rvm/gems/ruby-2.3.1/bin/popular-deals:22:in `<main>'                                                                                                        /usr/local/rvm/gems/ruby-2.3.1/bin/ruby_executable_hooks:15:in `eval'                                                                                                  /usr/local/rvm/gems/ruby-2.3.1/bin/ruby_executable_hooks:15:in `<main>'

i tried xpath, at_css, unless, if..else, doesn't help. also, don't error everytime, rid of it.

one way address problem bit paranoid:

@purchase_link = doc.at_css("div.detailleftcolumn a.success").try(:attr, "href")  deal[:purchase] = @purchase_link || @product_url

a couple of things keep in mind here. in ruby only nil , false logically false, it's rare need test nil? on things. case that's necessary when want distinguish between nil , false, can imagine not often.

so in case either hit at_css or didn't, in case try call doesn't anything. if finds try call carries on 1 more call. can assignment simple || (or) operator pick them in priority.

another thing since code inside class method, casually using instance variables can trouble. if things purchase_link used within method, remove @ makes them persistent.

another thing careful how method defined as:

def self.deal_page(input, product_url)

that declares argument product_url, inside:

html = open(@product_url)

this references class instance variable @product_url not same. may calling open wrong variable here.


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